1. Field of the Invention
The present invention relates to a glass forming apparatus and a glass forming method, and more particularly to an apparatus and a method of forming a glass substrate or a crystallized glass substrate for an information storage medium disk.
2. Related Art
Optical devices such as lenses and glass substrates for information storage medium disks and the like are usually manufactured by pressing and forming a glass ingot (molten glass) by either a direct press method or reheat press method.
The direct press method is a method of pressing and forming a glass ingot by using a die (a molding die, including upper die and lower die as described below), by lowering the temperature of a specified weight of molten glass to a forming temperature range. The reheat press method is a method of pressing and forming a glass ingot by a die, by reheating a specified weight of glass ingot obtained by cooling and solidifying molten glass, and heating up to a forming temperature range.
By the press forming method, in a process of obtaining a glass formed piece, such as a glass substrate for a lens or information storage medium disk, by press forming by a die for forming the glass ingot, the forming die receives heat from the molten glass. The forming die receiving heat has its temperature raised, and when glass formed pieces are manufactured continuously, a device for cooling the forming die is needed. If glass formed pieces are manufactured without cooling the forming die, the glass formed pieces may stick to the forming die, and the surface precision of the glass formed pieces is lowered significantly, and desired glass formed pieces cannot be obtained. Therefore, a glass forming apparatus capable of cooling the forming die is provided (see, for example, Japanese Unexamined Patent Application Publication No. H10-212127).
The glass forming apparatus disclosed in Japanese Unexamined Patent Application Publication No. H10-212127 has a heat exchange chamber in an upper die, and in the heat exchange chamber, a heat exchange fluid (for example, air containing water particles) for absorbing the heat around the press surface and cooling the press surface is fluidized and circulated.